import math
x1,y1,x2,y2=map(float,input().split())

l=math.sqrt((x2-x1)**2+(y2-y1)**2)

print('{:.8f}'.format(l)) import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 l=math.sqrt((x2-x1)**2+(y2-y1)**2) l math.sqrt((x2-x1)**2+(y2-y1)**2) math.sqrt math sqrt (x2-x1)**2+(y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 print('{:.8f}'.format(l)) print '{:.8f}'.format(l) '{:.8f}'.format '{:.8f}' format l y2=map(float,input().split()) map(float,input().split()) y2 y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 x2,y2=map(float,input().split()) map(float,input().split()) x2 x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 l=math.sqrt((x2-x1)**2+(y2-y1)**2) math.sqrt((x2-x1)**2+(y2-y1)**2) l
import math
x1,y1,x2,y2=map(float,input().split())

l=math.sqrt((x2-x1)**2+(y2-y1)**2)

print('{:.8f}'.format(l))
